1. Field of the Invention
This invention relates to a metering valve for delivering liquid vaporizable germicide to a sterilizer.
2. Description of the Related Art
Sterilization is used in a broad range of industrial and medical applications. Sterilization is the complete destruction or the irreversible inactivation of all the microorganisms in the system. Sterilization can be performed, for example, with heat or chemical treatment. Heat sterilization is normally done using steam. Some equipment cannot withstand the heat or the moisture of stem treatment. As a result, chemical sterilization is now commonly used.
Chemical sterilization can be done using alcohols, aldehydes such as formaldehyde, phenols, ozone, ethylene oxide, chlorine dioxide, or hydrogen peroxide. Hydrogen peroxide is commonly used for chemical sterilization.
U.S. Pat. No. 4,653,876, incorporated herein by reference, discloses an exemplary sterilization process in which a vaporizable germicide such as hydrogen peroxide is introduced into an evacuated sterilization chamber. The vaporizable germicide vaporizes and is allowed to disperse throughout the chamber and onto the items to be sterilized. After a period of time, electrical energy is applied to an electrode to form a plasma to complete the sterilization cycle.
The STERRAD(copyright) Sterilization System is an exemplary hydrogen peroxide sterilization system, commercially available from Advanced Sterilization Products, Irvine, Calif. Advanced Sterilization Products is a Division of Ethicon Endo-Surgery, Inc. The system employs an automated delivery system in which a measured amount of the liquid germicide, typically aqueous hydrogen peroxide, is delivered to the sterilization chamber. Measured portions of the liquid germicide are provided in rupturable cells within a liquid cassette housing. The cassette and the delivery system are fully described in the Williams et al. patents, U.S. Pat. No. 4,817,800, issued Apr. 4, 1989; U.S. Pat. No. 4,913,196, issued Apr. 3, 1990; U.S. Pat. No. 4,938,262, issued Jul. 3, 1990; and U.S. Pat. No. 4,941,518, issued Jul. 17, 1990, all of which are incorporated herein by reference.
Although the cassette and the delivery system work well, the delivery system is complex and expensive. There is a need for a delivery system which is simpler and less expensive than the cassette delivery system. Further, the volumes of vaporizable germicide which can be delivered to the sterilization chamber with the cassette delivery system are limited to incremental volumes of single cells on the cassette. For example, 1xc2xd cells of hydrogen peroxide cannot easily be delivered with the cassette delivery system. Because the amount of hydrogen peroxide required for sterilization depends on the size of the sterilization chamber, the quantity of equipment in the chamber to be sterilized, the materials from which the equipment to be sterilized is made, and many other factors, there are times when it would be useful to be able to add small additional increments of hydrogen peroxide into the sterilization chamber rather than being limited to adding an entire cell of vaporizable germicide from a cassette.
There is a need for a simple, inexpensive system for metering vaporizable germicide into a sterilization chamber in which the amount of vaporizable germicide can be varied in small incremental increments. There is a need for a simple vaporizable germicide delivery system which can deliver a wide range of volumes of vaporizable germicide to match the needs of various sizes of sterilization chambers.
One aspect of the invention involves a metering valve for delivering liquid to system. The metering valve includes a body having at least a first and a second orifice; and a rotatable valve plug located in the body, where the rotatable valve plug prevents direct fluid communication between the first orifice and the second orifice. The valve plug includes at least one well, where the well comes into fluid communication separately with the first orifice and the second orifice as the valve plug is rotated.
Advantageously, the orifices are located approximately 180 degrees apart in the valve body. The valve plug can be rotated manually or with a motor. In an embodiment, the valve plug includes at least two wells. The two wells may have different sizes or shapes. Preferably, the first orifice is never brought into direct fluid communication with the second orifice as said rotatable valve plug is rotated.
Another aspect of the invention involves a system for sterilizing equipment, where the system includes a metering valve. The metering valve includes a body with at least two orifices and a rotatable valve plug located in the body. The valve plug prevents direct fluid communication between the two orifices. The valve plug includes at least one well. The well comes into fluid communication separately with the two or more orifices as the valve plug is rotated. The system also includes a reservoir connected to a first orifice on the metering valve. The reservoir contains vaporizable germicide. The system also includes a sterilization chamber, where the sterilization chamber receives vaporizable germicide from a second orifice on the metering valve.
Preferably, the system also includes a vaporizer connected to the second orifice on the metering valve. The vaporizer is in fluid communication with the sterilization chamber. Advantageously, the system also includes a vacuum pump connected to the sterilization chamber. The system may include a source of plasma. An accumulator may be located between the second orifice on the metering valve and the sterilization chamber. An on/off valve may optionally be located between the metering valve and the sterilization chamber and/or between the metering valve and the reservoir. Advantageously, the vaporizable germicide is hydrogen peroxide.
Another aspect of the invention involves a method for sterilizing an article in a chamber. The method includes providing a source of vaporizable germicide, a chamber, and a metering valve for delivering germicide to the chamber. The metering valve includes a body having at least two orifices and a rotatable valve plug located in the body. The valve plug prevents direct fluid communication between the two orifices. There is at least one well in the valve plug. The well comes into fluid communication separately with the orifices as the valve plug is rotated. The metering valve is in fluid communication with the chamber and the source of vaporizable germicide. Rotating the valve plug transfers vaporizable germicide from the source of germicide into the well and from the well into the chamber.
Advantageously, the method also includes reducing the pressure in the chamber. Preferably, reducing the pressure vaporizes the vaporizable germicide, sterilizing the article in the chamber. In a preferred embodiment, the vaporizable germicide is accumulated in an accumulator located between the metering valve and the chamber. The article may be contacted with plasma. Preferably, the vaporizable germicide is hydrogen peroxide. The method may also include opening or closing a valve between the metering valve and the source of vaporizable germicide or between the metering valve and the chamber.